The present invention relates to a water tank for a transverse flow radiator and which comprises an overflow chamber partitioned from a main coolant stream collection chamber by a substantially vertical partition, with a secondary coolant stream passing through this overflow chamber into which opens a fill tube which is normally provided with a pressure relief valve.
Since the coolant circulating in the cooling system of, for example, an internal-combustion engine expands due to the heat of operation, it is customary in such radiators to provide an overflow vessel in which a volume of air is provided as a buffer. Generally, the fill tube for adding or replenishing coolant is also disposed at the overflow vessel as is a pressure relief valve which opens when a maximum permissible pressure in the cooling system is exceeded and initially permits part of the volume of air to escape. Radiators are also known which do not have a separate overflow vessel but in which this overflow vessel is integrated into the water tank as a compensation chamber which is separated from the main stream collecting chamber by a partition. In this case, the partition separating the overflow from the main stream collecting chamber must be fastened by a fastening process, for example by welding or soldering in heavy metal radiators. The attachment of the partition thus requires additional installation work in the production of the water tank.